Phthalyl-4-isothiocyanate → 5-Isothiocyanato-2-benzofuran-1,3-dione

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Reaction Steps

The 4-isothiocyanatophthalic acid thus obtained was immediately heated to reflux in a mixture of trifluoroacetic anhydride and methylene chloride for 2 hours under a nitrogen atmosphere. After cooling to room temperature, the reaction mixture was concentrated under reduced pressure. Recrystallization of the resultant solid from 30 mL of carbon tetrachloride afforded 4-isothiocyanatophthalic anhydride as brownish-purple crystals in a yield of 2.3778 g, (77 percent of theoretical). The title compound melted at 106°-108° C.; 1H NMR (300 MHz, acetone-d6) d, 8.15 (d, J=8.1 Hz, 1H), 8.06 (d, J=1.7 Hz, 1H), 7.97 (dd, J=8.1, 1.7 Hz, 1H); 13C NMR (75 MHz, acetone-d6) d 163.3, 162.6, 139.8, 134.8, 134.6, 130.6, 128.2, 123.5, 111.6; IR (CHCl3) 2010 (br), 1840, 1740 cm-1; MS m/e 205, 161, 133 (base), 74.

Provenance & Evidence